Existing tissue sample treatment methods, in some applications, comprise a number of steps that are performed manually. For example, in immunologic applications, such as in-situ hybridization (ISH) and immunohistochemical (IHC) applications, some steps, including baking a sample onto a slide, dewaxing, and epitope retrieval, are performed manually by an operator to treat the tissue sample before it can be used in a staining apparatus for staining the tissue sample according to a predetermined staining protocol.
Immunohistochemical staining and in situ nucleic acid analysis are tools used in histological diagnosis and the study of tissue morphology. Immunohistochemical staining relies on the specific binding affinity of antibodies with epitopes in tissue samples, and the increasing availability of antibodies which bind specifically with unique epitopes present only in certain types of diseased cellular tissue. Immunohistochemical staining involves a series of treatment steps conducted on a tissue sample (typically a section) mounted on a glass slide to highlight, by selective staining, certain morphological indicators of disease states.
Typical treatment steps include pre-treatment of the tissue sample to reduce non-specific binding, antibody treatment and incubation, enzyme labelled secondary antibody treatment and incubation, substrate reaction with the enzyme to produce a fluorophore or chromophore highlighting areas of the tissue sample having epitopes binding with the antibody, counterstaining, and the like. Between each treatment step, the tissue sample must be rinsed to remove unreacted residual reagent from the prior step. Most treatment steps involve a period of incubation typically conducted at ambient temperature of around 25° C. up to around 40° C., while cell conditioning steps are typically conducted at somewhat higher temperatures, e.g. 90° C. to 100° C. In-situ DNA analysis relies upon the specific binding affinity of probes (DNA binding proteins) with unique nucleotide sequences in cell or tissue samples and similarly involves a series of process steps, with a variety of reagents and process temperature requirements. Some specific reactions involve temperatures up to 120° C. to 130° C.
Attempts have been made to automatically treat tissue samples disposed on slides for immunologic applications using, for example, an automated tissue sample staining apparatus. In an existing example, the automated staining apparatus treats tissue samples using reagents to treat the sample before staining the samples on the slides. The treatment of the samples is performed automatically by one or more robots configured to dispense a plurality of designated reagents to slides in a predetermined sequence according to a staining protocol. In an existing example, the staining protocol uses high value reagents, such as antibodies, which are dispensed by a single robot in the staining apparatus one slide at a time. Due to the ever increasing numbers of histological test requests and biopsy samples, there are now significant pressures on laboratories to decrease turnaround time of treating tissue samples. Also, existing automated staining apparatuses tend to be bulky to accommodate the different treatment modules devoted to different treatment steps and thus take up a large amount of laboratory real estate.